1. Field of the Invention
The present invention relates to vacuum stage devices, and, more particularly, to a vacuum stage device that moves a substrate to be processed in a vacuum environment.
2. Description of the Related Art
To produce a semiconductor device, a number of manufacturing processes are carried out on a wafer (i.e., a semiconductor substrate), and there exist many kinds of semiconductor manufacturing processes that are carried out in a vacuum environment (i.e., in a vacuum processing chamber).
Specific examples of these semiconductor manufacturing processes include: a sputtering process for physically forming a thin film on a wafer; a CVD sputtering process for forming a thin film on a wafer by a chemical vapor technique; a lithography process for shaping thin films formed on a wafer; an impurity adding process for adding impurities to layers formed on a wafer that is an ion implantation process; an etching process for performing various etching operations on thin films formed on a wafer; an electronic beam process for performing a fine shaping operation on the surface of a wafer with an electronic beam; and an ion beam process for performing a fine shaping operation on a surface of the wafer with an ion beam. All of these processes are carried out in a vacuum environment.
When the above processes are carried out, it is necessary to move the wafer with precision in a vacuum processing chamber. Therefore, a transfer device for moving a stage (a base), to which the wafer is to be mounted, with precision in a vacuum processing chamber is provided for a processing device that carries out the above processes. In accordance with a process to be carried out for the wafer, the transfer device can selectively perform a moving operation in X-Y-Z directions, a tilting operation for tilting the wafer in relation to an electronic beam or the like, or a rotating operation for rotating the wafer.
Conventionally, a transfer device of this type for moving a wafer inside a vacuum processing chamber normally has a stage driving mechanism placed outside the vacuum processing chamber, for the following reasons:    1) It is difficult to employ a driving mechanism that generates heat, because the vacuum processing chamber does not contain a heat releasing medium (such as air) for releasing the heat generated by the driving mechanism to the outside.    2) As the volume of the vacuum chamber is reduced, the time required for obtaining a predetermined degree of vacuum can be shortened, and the throughput in the wafer processing can be increased. However, if the vacuum processing chamber is made smaller, the driving mechanism provided inside the vacuum processing chamber also becomes smaller. As a result, the driving force is lowered. For this reason, a wafer cannot be moved at a high speed inside the vacuum processing chamber, resulting in a reduced throughput.    3) Where a linear motor is employed as the driving mechanism, the wire rods that form the coil of the linear motor should be covered with a resin material for insulation purposes. Also, the coil is impregnated with resin and is thus solidified firmly, so as to prevent deformation due to a strong magnetic force between the wire rods or magnets. However, the heat, which is generated from the coil at the time of driving of the linear motor, generates outgas from the resin that is employed as the covering and solidifying material. As a result, the degree of vacuum inside the vacuum processing chamber is considerably lowered.
For the above reasons, the conventional stage driving mechanism is placed outside the vacuum processing chamber. In such a structure, it is necessary to introduce a stage driving force into the vacuum processing chamber from the outside. To do so, a vacuum sealing process needs to be carried out for the driving force introducing unit. As a result, the entire transfer device, as well as the vacuum processing chamber, becomes larger, and the production costs become higher.
Furthermore, if the stage inside the vacuum processing chamber is far apart from the stage driving mechanism placed outside the vacuum processing chamber, vibration and reaction force may be caused anywhere in the driving force transmission system that ranges from the stage driving mechanism to the stage. Because of this, it is difficult to move the stage at a high speed. If the moving speed of the stage (or the wafer) is reduced, however, the throughput of the wafer processing will drop considerably.